Ceramic wiring board, multi-piece ceramic wiring board, and method for producing same

Abstract

Provided are a ceramic wiring substrate; a multi-piece ceramic wiring substrate array for providing a plurality of the wiring substrates; and a method for reliably producing the wiring substrate array. The ceramic wiring substrate includes a substrate main body, which has a front surface, a back surface, side surfaces, a groove surface located on a side toward the front surface, and a fracture surface located on a side toward the back surface; and a notch which has a concave shape in plan view, and which is provided on at least one of the side surfaces so as to extend between the front surface and the back surface, wherein, in the side surface having the notch, the boundary between the groove surface and the fracture surface has curved portions on opposite sides of the notch, the curved portions being convex toward the front surface of the substrate main body in side view.

Description

TECHNICAL FIELD[0001]The present invention relates to a ceramic wiring substrate having few burrs in the vicinity of a notch provided on a side surface of a substrate main body, in which a conductor layer provided on the inner wall of the notch exhibits excellent solderability; to a multi-piece ceramic wiring substrate array for providing a plurality of the wiring substrates; and to a method for producing the multi-piece ceramic wiring substrate array.BACKGROUND ART[0002]Generally, ceramic wiring substrates are produced by separating a multi-piece ceramic wiring substrate array into individual pieces along separation grooves provided on the front surface or back surface of the wiring substrate array. In connection therewith, there has been proposed a method for producing a multi-piece wiring substrate array, in which a blade having a specific edge angle is pressed against a surface of a green sheet laminate at positions where separation grooves are to be formed, so that chips or bur...

AI Technical Summary

Benefits of technology

[0021]According to the first ceramic wiring substrate of claim 1 or the second ceramic wiring substrate of claim 2, since the boundary between the groove surface and the fracture surface has curved portions on opposite sides of the notch, the curved portions being convex toward the front surface of the substrate main body in side view, the groove surface has a tapered extending portion defined by an end of the bottom of the groove surface, the inner wall of the notch, and each curved portion. Therefore, since the fracture surface (i.e., a relatively rough surface) is not located in the vicinity of the notch, which is provided at a middle portion of a side surface of the substrate main body of the first or second ceramic wiring substrate, or at the corner formed by a pair of adjacent side surfaces of the substrate main body, generation of ceramic burrs or the below-described breakage of the conductor layer is completely or almost completely suppressed. In addition, since a plating film is formed so as to cover a cut surface (end surface) of the conductor layer formed on the inner wall of the notch, the cut surface being adjacent to the extending portion of the groove surface and being exposed to the outside, the ceramic wiring substrate exhibits improved reliability when it is mounted on a motherboard, etc. by soldering.

[0022]According to the ceramic wiring substrate of claim 3, a pair of groove surfaces are located on each side surface of the substrate main body on the front surface side and the back surface side so as to be in line symmetry with each other, and extending portions of each groove surface, which are provided on ends of the bottom of the surface, are located on opposite sides of the notch. Therefore, generation of burrs or the below-described breakage of the conductor layer is further suppressed. In addition, since a plating film is formed so as to cover a cut surface of the conductor layer formed on the inner wall of the notch, the cut surface being adjacent to the extending portion of each of the front-surface-side and back-surface-side groove surfaces and being exposed to the outside, the ceramic wiring substrate exhibits further improved reliability during mounting by soldering.

[0023]According to the ceramic wiring substrate of claim 4, since a plating film is formed so as to reliably cover a cut surface (end surface) of the conductor layer, the cut surface being adjacent to the extending portion of at least one of the front-surface-side and back-surface-side groove surfaces and being exposed to the outside, reliability is secured during mounting of the ceramic wiring substrate by soldering.

[0024]According to the multi-piece ceramic wiring substrate array of claim 5, the bottom of each of separation grooves which are formed on the front surface side of the product region and are arranged in a lattice shape in plan view has—at the end in the vicinity of the inner wall of a through hole crossing with the separation groove—a curved portion which is convex toward the front surface in side view, and which is located below the bottom and on the side toward the back surface. When the product region is folded along the separation grooves for formation of individual wiring substrate units, the aforementioned through hole becomes notches of side surfaces of adjacent ceramic wiring substrates, each of the notches having a concave shape in plan view, and one of the inner wall surfaces of each separation groove becomes a groove surface of the wiring substrate. Since the curved portion is formed as described above, the aforementioned burrs or breakage is less likely to occur at the bottom of the groove surface and in the vicinity of opposite sides of the notch. In addition, an extending portion including the curved portion is formed. Furthermore, since a cut surface of the conductor layer formed on the inner wall of the notch of each ceramic wiring substrate—the cut surface being adjacent to the extending portion and being exposed to the outside—is covered with a plating film (e.g., Ni plating film or Au plating film) provided before formation of individual ceramic wiring substrates, reliability is improved during mounting of the ceramic wiring substrate by soldering.

[0025]According to the multi-piece ceramic wiring substrate array of claim 6, the bottom of each of two pairs of separation grooves which orthogonally cross each other has—at the end in the vicinity of the inner wall of a through hole crossing with the separation grooves—a curved portion which is convex toward the front surface in side view, and which is located below the bottom and on the side toward the back surface. When the product region is folded along the separation grooves for formation of individual wiring substrate units, the aforementioned through hole becomes notches at the corner formed by adjacent side surfaces of adjacent ceramic wiring substrates, each of the notches having a quarter arc shape in plan view, and one of the inner wall surfaces of each separation groove becomes a groove surface of the wiring substrate. Since the curved portion is formed as described above, the aforementioned burrs or breakage is less likely to occur at the bottom of the groove surface and in the vicinity of opposite sides of the notch. In addition, an extending portion including the curved portion is formed. Furthermore, in a manner similar to that described above, the conductor layer formed on the inner wall of the notch realizes improvement of reliability during mounting of the ceramic wiring substrate by soldering.

[0026]According to the multi-piece ceramic wiring substrate array of claim 7, separation grooves formed on the front surface and back surface of the product region have—at ends in the vicinity of the inner wall of a through hole crossing with the separation grooves—a pair of curved portions which are in line symmetry with each other, which are convex toward the front surface or the back surface in side view, and which are located on the side toward the back surface or the front surface with respect to the bottom of each of the aforementioned separation grooves. Therefore, when the product region is folded along the separation grooves for formation of individual ceramic wiring substrates, generation of ceramic burrs or breakage of the conductor layer is further suppressed in the vicinity of the notch on a side surface of each ceramic wiring substrate. In addition, reliability during mounting of the ceramic wiring substrate by soldering can be further secured by means of the conductor layer formed on the inner wall of the notch.

Problems solved by technology

However, when separation grooves are formed in a green sheet by means of a blade through the production method described in Patent Document 1, since a fracture surface (cracking) meanders at the inner wall of a through hole which crosses with the thus-formed separation grooves in a radial direction of the through hole, irregularities or burrs are likely to be generated.

Therefore, the conductor layer may exhibit poor reliability during soldering for mounting of a component on the conductor layer.

Thus, the multi-piece wiring substrate array poses a problem in that various types of special blades are required, which results in considerably high production cost and low productivity.

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